De-icer

ABSTRACT

A chattering valve for use in a pulse pneumatic de-icer.

FIELD OF THE INVENTION

This invention relates to apparatus for de-icing leading edges. Moreparticularly, this invention pertains to the de-icing of aircraftleading edge surfaces such as are associated with wings, struts,stabilizers, and propellers. Specifically, this invention relates topneumatically actuated de-icers for use on leading edges.

BACKGROUND OF THE INVENTION

Since the early days of powered avaition, aircraft have been, from timeto time, troubled by accumulations of ice on component surfaces of theaircraft such as wings and struts, under certain flight conditions.Unchecked, such accumulations can eventually so laden the aircraft withadditional weight and so alter the aerofoil configuration of the wingsas to precipitate an unflyable condition. A search for means to combatthe accumulation of ice under flying conditions has been a continuingone and has resulted in three generally universal approaches to removingaccumulated ice, a process known generally as de-icing.

In one form of de-icing, leading edges, that is edges of the aircraftcomponent on which ice accretes and are impinged upon by the air flowingover the aircraft and having a point at which this airflow stagnates,are heated to loosen adhesive forces between accumulating ice and theaircraft component. Once loosened, this ice is generally blown from theaircraft component by the airstream passing over the aircraft. Twomethods of heating leading edges have enjoyed significant popularity. Inone approach a heating element is placed in the leading edge zone of theaircraft component either by inclusion in a rubber boot applied over theleading edge or by incorporation into the skin structure of the aircraftcomponent. This heating element, typically powered by electrical energyderived from a generating source driven by one or more of the aircraftengines, is switched on and off to provide heat sufficient to loosenaccumulating ice. In small aircraft powered typically by one or twoengines, a sufficient quantity of electrical power may be unavailablefor use in electrical de-icing.

In the other heating approach, gasses at elevated temperature from oneor more compression stages of a turbine engine are circulated throughleading edges of components such as wings and struts in order to effecta thermal de-icing or anti-icing effect. Employed typically only inaircraft powered by turbine engines, the use of these so-calledcompressor bleeds or by-pass streams from the aircraft engine turbinecan result in reduced fuel economy and a lower turbine power output.

The second commonly employed method for de-icing employs chemicals. Inlimited situations a chemical has been applied to all or part of theaircraft to depress adhesion forces associated with ice accumulationsforming upon an aircraft or to depress the freezing point of watercollecting upon surfaces of the aircraft.

The remaining commonly employed method for de-icing is typically termedmechanical de-icing. In the principal commercial mechanical de-icingmeans, pneumatic de-icing, the leading edge zone of a wing or strutcomponent of an aircraft is covered with a plurality of expandable,generally tube-like structures inflatable employing a pressurized fluid,typically air. Upon inflation, the tubular structures tend to expandsubstantially the leading edge profile of the wing or strut and crackice accumulating thereon for dispersal into the airstream passing overthe aircraft component. Typically, such tube like structures have beenconfigured to extend substantially parallel to the leading edge of theaircraft component. For aerofoils such as wings and stabilizers, thesestructures may extend the entire span of the aerofoil. A plurality oftube-like structures frequently are positioned on a wing or strut andtypically are configured to be parallel to the leading edge of the wingor strut as by placement of a spanwise succession of tubes spaced inchordwise manner away from the leading edge. The plurality of tubes canprovide an ice removal function to the entire leading edge profile ofthe aerofoil or strut.

Conventionally, pneumatic de-icers are formed from a compound havingrubbery or substantially elastic properties. Typically, the materialforming tubes on such de-icer structures can expand or stretch by 40% ormore during inflation cycles causing a substantial change in the profileof the de-icer (as well as thereby the leading edge) and therebycracking ice accumulating on the leading edge. At least in part becauseof the large volume of air required for inflating such highly expandabletubes, the times for inflating such tubes have typically historicallyaveraged between about 2 and about 6 seconds. The distortion engenderedin an aerofoil profile by inflation of the tubes can substantially alterthe airflow pattern over the aerofoil and can adversely effect liftcharacteristics of the aerofoil.

The rubber or rubber like materials forming these conventional pneumaticde-icers typically are possessed of a modulus of elasticity ofapproximately 6900 kPa. Ice, as is well known, is possessed of anelastic modulus enabling typical ice accumulations to adjust to minorchanges in contours of surfaces supporting such ice accumulations. Themodulus of elasticity for ice is variously reported as being betweenabout 275,000 kPa and about 3,450,000 kPa. The modulus of elasticity ofrubber compounds used in conventional de-icers however is substantiallydifferent from the modulus of elasticity typically associated with iceaccumulations, and the large, 40% or greater expansion undergone by thede-icer during inflation traditionally has functioned to crack orrupture the structure of the ice accumulations thereon allowing suchaccumulations to be swept away by impinging wind streams.

Ice accumulations, in conforming to minor alterations in the contours ofsurfaces supporting the ice accumulations do so only somewhat slowly.The phenomenon by which ice accumulations conform to changing contoursof support surfaces in some ways may resemble the phenomenon of coldflow in thermoplastic materials. Where the ice accumulations are exposedto extremely rapid but minor deformations, an ice coating cannotaccommodate such contour changes sufficiently rapidly and shatters asthough struck with a hammer. More recently, it has been discovered thata subjecting leading edges of a wing or a stabilizer toelectromechanical induced hammering, such as is shown by U.S. Pat. No.3,549,964, can assist in removing accumulations of ice on the leadingedge. Concern respecting the susceptibility of such leading edges tostress fatigue upon being hammered over extended periods of time as yethave functioned in part to preclude substantial commercial developmentof such electromechanical hammering schemes.

A means for de-icing a leading edge not requiring the application ofelectrothermal de-icers and/or not requiring the application ofpneumatic de-icers which, during the inflated state, substantiallydistort the leading edge profile for an extended period of time therebyinterfering with the efficient performance of a device associated withthe leading edge could find substantial application in industry.Additionally, where such a means for de-icing a leading edge does notpose a significant likelihood for long term structural damage associatedwith stress or fatigue such as may be associated with electromechanicalhammering, such a de-icing means could find substantial commercialutility.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for de-icing ice accretingsurfaces and finds particular utility in the de-icing of aerofoilsleading edges, struts and the like associated with aircraft. The de-icerof the present invention includes a sheet-like skin possessed of asubstantially elevated modulus and formed into a desired configurationhaving an ice accreting surface associated therewith. The de-icerfurther includes a support surface separate and apart from the skin andpositioned obversely with respect to the ice accreting surface.

At least one principal inflation tube is positioned between the supportsurface and the skin. A means is provided for introducing a fluid underpressure into the principal inflation tube in a quantity sufficient toinflate the principal inflation tube to a desired extent at whichdesired deformation of the skin occurs to a degree sufficient to detachand then dislodge or expel ice accumulations upon the ice accretingsurface into a stream of fluid flowing over the ice accreting surface.Yet inflation is not accomplished to an extent sufficient to exceed astress level characterizing an endurance limit for the material formingthe skin. A means is provided for subsequently deflating the principalinflation tube.

The de-icer of the invention may include a plurality of additionalinflation tubes positioned between the support surface and the skin andconfigured, likewise, for inflation to an extent sufficient to deformthe skin to a degree sufficient to dislodge ice accumulations upon theice accreting surface thereover without exceeding stress endurance limitfor the material from which the skin is formed.

In the practice of the invention, the principal inflation tube or tubestypically are formed from at least one ply of a fabric coated on atleast one surface with a rubberizing or plasticizing compound, andformed and vulcanizably cured or thermoplastically molded as isappropriate to define the principal inflation tube. Typically, anyprincipal inflation tube is affixed to the support surface.

In the practice of the invention, it may be desirable to include a plypositioned intermediate the skin and the support surface to lie betweenthe principal inflation tube and the skin. The additional inflationtubes may be attached to this intermediate ply and configured to lieeither between the intermediate ply and the skin or between theintermediate ply and the support surface.

In the practice of the invention, it may be desirable to interconnectthe principal inflation tube or tubes with the additional inflationtubes whereby a fluid under pressure employed to inflate the principalinflation tube can thereafter pass into and be employed to inflate theadditional inflation tubes. In the practice of the invention, it may bedesirable to inflate the principal inflation tube(s) are joined to thewithin not more than 0.25 seconds. Where the principal inflation tube(s)are joined to the additional inflation tubes for inflation of theadditional inflation tubes employing the fluid under pressure used toinflate the principal inflation tube(s), following inflation of theprincipal inflation tube within the 0.25 seconds, the additionalinflation tubes typically become inflated more slowly and can functionthereby to partially de-pressurize the principal inflation tube(s) ifdesired.

In certain preferred embodiments a pulse of fluid partially inflates theprincipal tube(s) causing the high modulus skin to dislocate and thenstop suddenly. Momentum imparted to the ice accumulations thereby causesadditional ice movement which assists in ice detachment and dislodgment.Additional further inflation in staged pulses can further enhanceeffective ice removal. Use of a valve for inflation characterized by achattering mode of operation can be effective in achieving such a"start-stop" inflation pattern.

Typically, the skin is an outer skin defining a leading edge of anaerofoil such as an aircraft wing, aileron, propeller, rotating wingsuch as a helicopter rotor or tail or tail rotor. The skin preferably isformed of titanium, aluminum, steel, including stainless steels, highmodulus polymers, and elevated modules polymeric composites, allelevated modulus materials.

In the method, at least one principal inflatable tubular structure isperiodically inflated and deflated in a cavity between the skin and thesupport surface for the principal inflatable tubular structure.Inflation is accomplished employing a fluid under pressure. Thesufficient extent to detach and dislodge accreted ice but insufficientlypressurized whereby stresses placed upon the skin do not exceed anendurance limit for the material from which the skin is formed.

In preferred embodiments the invention a pair of principal tubularstructures are inflated between the support surface and the skin, theprincipal tubular structures being spaced apart one from the next to anextent sufficient to assure that upon inflation, bending distortion ofthe skin by reason of such inflation does not exceed a microstraincharacterizing a substantial likelihood of fatigue failure for the skinwithin a million inflation/deflation cycles of the tubes. Preferably, anadditional plurality of tubes between the support surface and the skinare inflated in coordinated manner with the principal inflation tube toproduce a distortion of the skin thereover sufficient to detach anddislodge accumulations of ice thereon. In certain preferred embodimentsof the invention, the inflatable tubular structures are inflated withinnot more than about 0.10 seconds and preferably not more than about 0.50milliseconds. Pulsating inflation is contemplated as within the purviewof the invention.

The above and other features and advantages of the invention will becomemore apparent when considered in light of a description of a preferredembodiment of the invention together with drawings which follows forminga part of the specification.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of an aircraft wing incorporating ade-icer in accordance with the invention.

FIG. 2 is a control schematic for controlling activation of de-icers inde-icing a surface in accordance with the instant invention.

FIG. 3 is a depiction of an alternate de-icer tube configuration for usein the wing of FIG. 1.

FIG. 4 is a cross-sectional representation of an alternate embodiment ofa de-icer in accordance with the invention.

FIG. 5 is a schematic of an inflation tube arrangement.

FIG. 6 is an alternate of an inflation tube arrangement.

FIG. 7 is a depiction of a valve suitable for use in inflating theprincipal inflation tube(s).

BEST EMBODIMENT OF THE INVENTION

The present invention provides an apparatus for de-icing a leading edgesurface. By "de-icing" what is meant is the removal of ice subsequent toformation of the ice upon the leading edge. By "leading edge" what ismeant is that portion of a surface of a structure which functions tomeet and in substantial measure break, an airstream impinging upon thestructure. Examples of leading edges would be forward edge portions ofwings, stabilizers, struts, nacelles, propellers, rotating wings such ashelicopter rotors, tail rotors and other housings, objects andprotrusions first impacted by an airstream flowing over an aircraft inflight as well as spars, struts and other structural elements of marinevessels, towers and buildings.

Referring to the drawings, FIG. 1 depicts one embodiment of an aircraftwing leading edge de-icer 10 in accordance with the invention.

The de-icer 10 includes an outer layer or skin 12 formed of asubstantially rigid material such as a plastic or metal having asubstantially elevated modulus of elasticity or so-called Young'smodulus. This modulus of elasticity should be at least 40,000 kPa.Preferably this modulus of elasticity approaches or exceeds the modulusof elasticity associated with ice accumulating upon the leading edge, sothat preferably this modulus of elasticity is at least 275,000 kPa. Inmost modulus of elasticity may extend to encompass about 7,500,000 kPaor greater.

A principal inflatable member 14 and a support surface 16 are providedwith the principal inflatable member 14 typically being affixed byadhesion or other suitable or conventional means to the support surface16. It should be apparent that the outer skin 12 can be formed as partand parcel of an aircraft skin 12' defining the outer contour of thewing, can be attached to the aircraft skin 12', or can be separatelyattached to the aircraft with the support surface 16 instead being partand parcel of the aircraft skin 12'. In the embodiment of FIG. 1, thede-icer skin 12 is shown as part and parcel, that is a continuation of,the aircraft skin 12'.

The principal inflatable member 14 is a tube-like structure typicallyrunning the length of the de-icer 10 and formed of a fabric materialcoated on at least one surface with a rubberizing compound orplasticizing. The tube 14 is formed so that the surface coated with therubberizing or plasticizing compound faces outwardly from the center ofthe inflatable member 14 and therefore defines inflation chamber orcavity 18 within the tubular member 14. Suitable materials andtechniques for the forming of tubular members from rubberized orplasticized fabric are known in the art of rubberized and plasticizedfabric working. An inflation conduit 20 is provided fluid communicationwith the inflation chamber 18 in suitable or conventional manner.

Only a single principal inflation member 14 is depicted in FIG. 1. Itshould be understood that a plurality of principal inflation members ora plurality of chambers within a single principal inflation member 14may be positioned between the outer skin 12 and the support surface 16and configured for inducing distortion of the outer skin upon inflation.As shown in FIG. 3 for example, the inflation tube 14 can be stitched toprovide a pair of parallel inflation chambers 18, 18' with fluidcommunication therebetween via the stitching. Where the stitching issealed or adhesive or chemical bond substituted for the stitching a pairof parallel inflation tubes result.

Referring again to FIG. 1, an upper intermediary ply 24 and a lowerintermediary ply 26 are positioned beneath the skin 12. These plies 24,26 are suitably formed of a fabric material coated on one surface with arubberizing or plasticizing coating compound in well-known manner. Inthe upper intermediate ply 24, the rubberizing or plasticizing coatingfaces in a direction outwardly towards the skin 12 and the ply 24 isbonded to the skin 12. In the lower intermediate ply 26, the rubberizingor plasticizing coating compound faces in a direction inwardly away fromthe skin whereby the uncoated fabric or sides or surfaces of theintermediate plies 24, 26 cooperate to define an interstitial space 28between the plies 24, 26.

The fabric employed in the intermediate plies 24, 26 may be of anysuitable or conventional nature. Preferably a rayon, polyester, aramid,nylon or acrylic fiber-based fabric is employed. The rubberizing orplasticizing compound can be of any suitable or conventional nature suchas natural, synthetic, styrene-butadiene or chloroprene rubbers andplasticizing thermoplastic or plasticizing thermosetting resins as theseterms are known in the art and useful mixtures thereof, all as suitablefor bonding to the outer skin 12 or to other structural components ofthe de-icer 10. Appropriate rubberizing compounds and plasticizingcompounds are well-known in the rubber and/or plastic compounding field.

The plies 24, 26 may be joined by mechanical or chemical attachment suchas by heat sealing, chemical bonding, adhesives, or, as shown by thedrawing in FIG. 1, by stitching 29 adjacent at least one trailing edge30 of the de-icer.

Optionally, a bonding ply 36 is provided and the principal inflationmember 14 is affixed to the bonding ply 36. Affixation can beaccomplished by adhesion, vulcanized bonding, or other suitable orconventional method. The bonding ply 36 typically is formed from rubberor a rubber-like material such as a plasticizing compound that mayinclude a fabric reinforcement, the rubber or rubber-like material beingselected as suitable for bonding to the support surface 16. Suitable orconventional rubber or rubber-like plasticizing materials are well-knownin the art and the selection of a particular compound or fabric materialtypically is predicated upon a number of factors which may include thenature of the support layer 16 to which the bonding ply 36 is affixed,and the relative cost and availability of various fabrics and of naturaland synthetic rubbers or plasticizing rubber-like agents. Chloroprenessuch as NEOPRENE® (duPont) and nitrile rubbers are preferred as bondingply 36 rubber materials.

The principal inflatable member 14 is of a size and shape such that wheninflated to a desired pressure, typically between about 69 and 276 kPa,the outer skin 12 is deformed above the tubular member to an extent ofnot more than about 0.5 centimeters and preferably not more thanapproximately 0.25 centimeters. The actual distortion required is inpart a function of the physical configuration for leading de-icer 10 andthe nature of ice deposits formed thereon. Typically such distortionsare desirable in a range of between 0.1 and 0.35 centimeters. Bydeformed or distorted what is meant is movement of a point on thede-icer 10 outer skin 12 from a physical location while the principalinflation tube is placid to a physical location once the principalinflation tube has been inflated to the desired extent and pressure.

Distortion of the outer skin pursuant to inflation of the principaltubular member 14 produces chordwise strain depicted in FIG. 1 by lines35 in the outer skin 12. This distortion and the accompanying chordwisestrain eventually reaches a point where stresses develop at theinterface between ice and the outer skin 12 which stresses serve tobreak the adhesive bond of the ice to the skin thereby detaching theice, and develop cohesive fractures in the ice itself due, it isbelieved, to an inability of the ice to accommodate rapidly strain tothe extent of the rapidly induced strain in the skin 12 to which the iceis attached. At the same time the inflation action produces a distortionmotion in the skin 12 and ice and momentum thereby is applied to theice. As the skin stops moving when inflation is completed, the icemomentum functions to dislodge and eject the detached ice from the skin12.

Where inflation is accomplished slowly. insufficient momentum may not beimparted to the ice to secure dislodgment or ejectment of the detachedice absent the existence of additional forces. Such forces can includecentrifugal force associated with motion of propellers or rotating wingsand tail rotors or distortional turbulence in an airstream impinging theleading edge.

The use of step-off filets 37, 38 may be desirable in assuring auniformly smooth profile for the de-icer 10 as depicted in FIG. 1.

The chordwise strain depicted by the lines 35 in FIG. 1 imparts acertain, very limited stretching motion in the outer de-icer skin 12.Stretching in the outer skin 12 is limited because, unlike conventionalpneumatic de-icers, the outer skin is possessed of a high moduluselasticity. High modulus considerations are not important with respectto the rubberized intermediate plies 24, 26, if used, and the bondingply 36, if present, which are intended to be substantially low modulus.Modulus considerations are very important however for the outer skin 12and typically are important for the support layer 16 which are bothintended to be formed of material having a substantially high modulus.Accordingly, the outer skin is formed of a substantially high modulusmaterial having an ultimate elongation necessarily greater than that ofthe ice accumulations preferably greater than about 1/4% and mostpreferably greater than about 1/2%. By ultimate elongation what is meantis the percentage of permanent deformation remaining after tensilerupture. The operational elongation to which the outer skin 12 issubjected, that is elongation strain associated with routine, ordinaryoperation of the de-icer, as a result of chordwise strain represented bythe lines 35 in FIG. 1 should be comfortably less than the ultimateelongation inherent to the material forming the outer skin 12 definingthe outer surface of the de-icer. Where the operational elongationexceeds the ultimate elongation, premature and potentially catastrophicfailure of the outer skin 12 may occur. Equally important, theoperational elongation should not induce or effect a strain as depictedby the lines 35 in excess of a strain associated with early fatiguefailure of the material forming the skin, again to avoid premature andpossibly catastrophic failure.

Likewise, the support ply 16 or layer must be formed of substantiallyhigh modulus materials to assure against detrimental or deleteriousdeformation of the support ply during inflation of the principalinflation tube 14 and leading therefore to a failure to adequatelystrain the outer skin 12.

The outer skin 12 may be formed from suitable or conventional materialssuch as metals or plastics. Thin sheets of stainless steel, annealedstainless steel, thin sheets of titanium or annealed titanium and to alesser extent aluminum are of great utility in the practice of theinvention as having a very desirable Young's modulus. Plastics havingthe characteristic of a high modulus of elasticity or Young's modulusand a suitable ultimate elongation find utility in forming an outerskin.

By "thin" what is meant is 0.00254 to about 0.0254 centimeters formetals and 0.008 centimeters to 0.0508 for non metals. One plasticmaterial finding particular use in the practice of the invention ispolyetheretherketone (Peek) available from ICI. Other suitable orconventional plastic material such as polycarbonates, acetals, nylons,polyesters, polyvinyl fluorides, polyethylenes, epoxy resins formed intocomposites as well as pherrolic resins formed into composites and thelike can be employed in the practice of the instant invention. Suchmaterials will possess an ultimate elongation greater than about 3.0%and preferably greater than about 5.0% and an elastic modulus or Youngsmodulus of at least about 40,000 kPa and preferably at least about275,000 kPa but up to about 7,500,000 kPa or more. The use of certainpolymeric materials in lieu of metals in forming the skin 12 may beadvantageous due to a lower tendency for ice to adhere to such polymericmaterials. The outer skin 12 of the de-icer 10 can define a structuralleading edge, thus performing a dual role.

While it had previously been a generally accepted postulation that highmodulus materials must be their nature require de-icing employing anextremely rapid deformation, it is a feature and advantage of thepresent invention that deformation can be accomplished at a moremeasured pace. Accordingly, and surprisingly, inflation rates or timescharacterizing priorly known highly elastic pneumatic de-icers mountedupon ice accreting surfaces of wings can also be employed with respectto the principal inflation tube 14 associated with the instantinvention. As though the principal inflation tube 14 may inflate over aperiod of time as long as between about one and about five seconds.Nonetheless and notwithstanding relatively slow but full inflation ofthe principal inflation tube 14, the strain placed thereby upon the skin12 is sufficient to detach and assist in dislodging ice accumulationsthereon notwithstanding the substantially elevated modulus of elasticityassociated with the skin 12. The presence of additional forces such asrotational motion of the leading edge or turbulent disturbances in theairstream flowing over the leading edge may be required to assure acomplete dislodging of all ice so detached. These results would appearto be contrary to all the prior teachings in the art with respect tode-icing as a function of gradual deformation of an ice accretingsurface.

In the practice of the invention, it is of course equally possible thatthe principal inflation tube be inflated in such a manner thatdeformation of the outer skin 12 to a degree sufficient to discharge iceaccumulations thereon can be accomplished in less than the about one tofive seconds associated with ordinary pneumatic de-icers, moreparticularly in less than 0.10 seconds, preferably less than 50milliseconds, and most preferably less than 20 milliseconds. Pulsatinginflation has been particularly effective where shorter inflation timesare employed. Particularly where centrifugal or turbulent airflowforces, for example, are available, it is not essential that inflationof the principal inflation tube 14 to the desired extent to effectdetachment and discharge of ice upon the skin 12 be accomplished in lessthan the time ordinarily associated with the inflation and deflationcycle of a conventional pneumatic de-icer. While both rapid and moreleisurely inflation cycles can function to remove ice accumulations of athickness of 0.6 centimeters or less, it has been found that iceaccumulations of less 0.05 can, surprisingly, be effectively removed bya relatively slower inflation/deflation cycle for the principalinflation tube 14 much akin to the more rapid inflation mode where theinflation tube is inflated to a desired extent in a relatively shortperiod of time such as less than 0.10 seconds, preferably less than 50milliseconds or most preferably less than 20 milliseconds. While suchvery short inflation/deflation cycles can function to, in thevernacular, blast rather thick ice accumulations from the outer skin 12,it has been found that a slower inflation/deflation cycle may be undermany circumstances, as effective in removing very thin ice layers. Suchremoval is particularly advantageous where additional forces are presentsuch as in conjunction with propeller or rotating wing de-icing.

Where the principal tubular member 14 as shown in FIG. 1 is inflatedemploying a fluid under pressure at rates more characteristic ofconventional de-icers, that is 0.50-5 seconds, the pressurizing fluidcan be introduced in a suitable or conventional manner. Typically,pressurized fluid is introduced along a conduit 20 in well-known mannerto the principal inflation tube 14. Where a source of fluid, such asair, under pressure is employed via the conduit 20 to inflate thetubular inflation chamber 18, the source of fluid under pressure can beregulated to provide a fluid pressure not greater than that necessary toachieve a desired degree of inflation to effectively removeaccumulations of ice from a surface 13 of the de-icer 10. For rapidinflation modes, preferably a source of fluid under pressure greaterthan the pressure normally associated with desired full and finalinflation of the principal tubular member 14 can be employed. Where suchhigher pressure fluid sources are employed, it is typically advantageousto include a positive means for preventing over-inflation/pressurizationof the principal tubular member 14 thereby forestalling structuraldamage to the support surface 16 and the outer skin 12. Fluid underpressure can be provided in any suitable or conventional manner such asby an air compressor (not shown) or compressed gas cylinder (not shown)aboard an aircraft. Alternately, air at low pressure suitable forinflating the principal tubular member 14 of the instant invention at0.5-5 second rates can be obtained employing a bypass bleed from one ormore compressor stages associated with a turbine engine aboard anaircraft.

In the embodiment of FIG. 1 it may desirable to provide a conduit 31 bywhich interstitial pressure within the cavity 28 can be bled. Such ableed provision assists in assuring against a build up of pressurebetween the outer skin 12 and the support surface 16 that mightotherwise interfere with desirably full inflation of the principaltubular member 14. It may be desirable to join the conduit 31 to asource of vacuum whereby the interstitial space can be maintained undervacuum.

In the event it is desired that the tubular inflation chamber 14 beinflated quite rapidly, that is in less than about a second andpreferably less than about 0.10 seconds, rapid inflation can beaccomplished employing a source of high pressure air and a controlschematic as shown in FIG. 3. Referring to the drawings, FIG. 2 depictsa schematic for a system 80 in accordance with the invention forde-icing wings and horizontal stabilizers of an aircraft. The system 80includes a source 81 of low pressure air such as a compressor or a bleedfrom a jet engine turbine stage. The source 81 is joined to regulators82, 83 for assuring a constant supply pressure of the low pressure airsource. The regulator 83 is configured to supply low pressure air to anejector; the regulator 82 is configured to supply an intensifier 84. Asuitable intensifier is disclosed in U.S. application Ser. No.06/822,972 now U.S. Pat. No. 4,706,911 issued, Nov. 17, 1987.

High pressure air in the main accumulator 85 is available throughsuitable conduits 86 to accumulators 50 associated with pilot valves 52.The high pressure air from the accumulator 50 is then made available toindividual wing and stabilizer de-icers 87, 88, 89 having principalinflatable members 14 such as are depicted in FIG. 1.

A control device 90 functions to control the activation of the solenoids59 associated with the pilot operated valve 52 whereby timed release ofhigh pressure air to the principal inflatable members 14 of the de-icers87, 88, 89 can be accomplished. Such control can be accomplished inwell-known fashion.

It should be understood that the system 80 depicted in FIG. 2 isexemplary only, and that various modifications and alterations may bemade thereto in accommodating particular de-icer configurations and thephysical valving configurations necessary to supply fluid under pressurethereto. In particular, the low pressure source 81 of air can bereplaced by a high pressure source of air such as from a compressor (notshown) or a storage gas bottle (not shown) whereupon the intensifier 84may become superfluous. Also, the vacuum regulator 83 and the regulator82 may consist of a single unit supplying low pressure air for vacuumproduction and for intensification.

Referring to the drawings, FIG. 3 depicts a preferred alternateembodiment of the instant invention wherein the skin portion 12' of theaircraft does not surround the inflation tube 14 in defining the outerskin 12 and wherein the support surface 16, in contrast to FIG. 1, is acontinuation of the structure of the skin portion 12'. No intermediateplies 24, 26 are employed in the embodiment depicted in FIG. 5 and theinflation tube 14 is adhered to the support surface 16 in suitable orconventional manner such as by adhesive techniques.

In the embodiment of FIG. 3, the principal inflation tube 14 issubdivided by stitching 21 to form a pair of parallel tubular chambers18, 18'. The stitching is of a sufficient breadth to define a stitchzone 21' whereby upon inflation of the chambers 18, 18' bending stressesin the skin 12 immediately above the stitch zone 21' engendered byreason of inflation of the chambers 18, 18' does not exceed an endurancelimit for the material from which the skin 12 is formed. The stitch zone21' establishing a spacing between the tubes 18, 18' will of course varydepending in part upon the material forming the skin 12 since variousskin materials will have various endurance limits. The stitching 21equally could be a zone of adhesion or chemical bonding.

By "endurance limit" what is meant is a capability for withstanding atleast a million cycles of inflation/deflation of the tubular inflationchambers 18, 18' without significant risk of a brittle or a stressfracture or yielding in the skin 12. The identification of an endurancelimit for a particular material and the determination of bendingstresses engendered by a particular spacing of the tubular inflationchambers 18, 18' is within the purview of the skill and knowledge of onefamiliar with the art of strength of materials.

Referring to the drawings, FIG. 4, is a depiction of a further preferredembodiment of the invention wherein an aircraft leading edge is shown incross-section having a de-icer outer skin 12 having an ice accretingsurface 13, an obverse surface 15, and a support surface or layer 16supporting a principal inflation tube 14 having an inflation chamber 18.An intermediate ply 24 lies between the support surface 16 and theobverse surface 15 of the skin 12. No intermediate ply 26 is employed inthe embodiment of FIG. 4. The principal inflation tube 14 lies betweenthe intermediate ply 24 and the support surface 16.

In FIG. 4 plurality of additional inflation tubes or tubular members 27are provided between the intermediate ply 24 and the obverse surface 15.The additional tubular members 27 are configured to, upon inflation,exert de-icing stresses upon the outer skin 12 immediately thereover.The additional tubular members 27 can be of any suitable or conventionalnature and typically are formed in a manner similar to the inflationtube 14.

Referring to FIG. 4, it should be apparent that the additional tubularmembers 27 need not lie between the intermediate ply 24 and the skin 12obverse surface 15, but rather could lie between the support surface 16and the intermediate ply 24. It should be apparent that the intermediateply 24, depending upon desired configuration, may not be necessary, andtherefore both the principal tubular member 14 and the additionaltubular members 27 can lie or be positioned or affixed upon the supportsurface 16 for direct contact and interaction with the outer skin 12obverse surface 15.

Referring again to the drawings, FIG. 5 is a representation of a meanssuitable for inflating the additional tubular members 27. The additionaltubular members 27 are configured in fluid communication with theprincipal inflatable principal tubular member 14 whereby fluid inflatingthe tubular member 14 can thereafter fill and inflate the additionaltubular members 27. Where it is desired that fluid under an elevatedpressure be employed to inflate the principal inflatable tubular member14, it is desirable that the passageway 32 for each additional tubularmember 27 be configured to restrict the flow of fluid into theadditional inflatable tubular members 27 so that the principal inflationtube 14 can inflate virtually instantaneously with a pressure "snap"prior to significant inflation of the additional tubular members 27. Thesizing of a particular restricted passageway 32 is within the purview ofone skilled in the art of fluid dynamics.

Referring to FIG. 5, it should be readily apparent that the additionalinflatable tubular members 27 need not be inflated employing fluidderived from a filling of the principal inflatable tubular member 14.Referring to FIG. 6 the additional inflatable tubular members 27 can beeach inflated employing the source of fluid under pressure through aseparate inflation conduit 20 in well-known manner or may be joined to aheader (not shown) supplied with fluid under pressure from a sourcethereof also in well-known manner. The selection of a particular meansfor inflating the additional tubes 27 is at least in part a function ofweight considerations, orientation of the additional tubes 27 withrespect to the principal inflation tube 14 (that is whether generallyparalleling or lying generally perpendicualr to the principal inflationtube), and the nature and manner in which the principal inflation tube14 is to be inflated as well as the sequence, if any, in which theprincipal inflatable tubular member 14 and the additional inflatabletubular members 27 are to be inflated.

In operation, the de-icer of the invention is inflated and deflated in acyclical manner to remove ice accumulation on the ice accreting surface13. Where only a single principal inflatable tubular member 14 isemployed, the principal inflatable tubular member 14 is alternatelyinflated and deflated to cause distortion to the outer skin 12sufficient to remove ice accumulation on the ice accreting surface 13thereof without exceeding an endurance limitation for the material fromwhich the outer skin is formed. Typically, a time-period often manytimes longer than the inflation/deflation cycle for the principalinflatable tubular member 14 is provided between discrete inflationperiods for the principal inflatable tubular member 14. In otherembodiments, it may be desirable alternately to inflate and deflate theprincipal inflatable tubular member 14 virtually continuously or toinflate the principal inflatable member 14 in small spurts or surges.Generally the longer the time period between inflation cycles for theprincipal tubular member 14, the greater an ice accumulation thicknessdeveloping upon an ice accreting surface 13 and requiring removal. Ofcourse with greater ice accumulation thicknesses generally goes agreater interference with efficient aerofoil performance.

Where additional inflatable tubular members 27 are employed, theseadditional inflatable tubular members 27 may be inflated concurrentlywith the principal inflatable tubular member(s) 14, may by the useappropriate restricting passageways 32, be inflated slightlysubsequently to inflation of the principal inflatable tubular member(s)14, or further alternately may be inflated separately from the principalinflatable tubular member 14 optionally on an inflation cycle whollydifferent from that characterizing the principal inflatable tubularmember 14. Typically, where the members 14, 27 are inflated in acoordinated manner, the principal inflatable tubular member 14 isinflated first and then either deflated, or maintained in an inflated orpartially inflated state while the additional tubular members 27 aresubsequently inflated and then deflated. The particular cycle ofinflation/deflation for all the members 14, 27 will to some extent be afunction of the nature of the aerofoil or other surface being de-icedand the nature and extent of stress that can be accommodated by aparticular material of construction forming the skin 12 and defining theice accreting surface 13.

Where it is desired that the principal inflatable tubular member 14 beinflated extremely rapidly, that is in less than 0.10 seconds and morepreferably in less than 0.50 milliseconds, it may be particularlyadvantageous to employ the interconnected additional tubes shown in FIG.5 together with the restricted passageway 32 shown in FIG. 5 to effectinflation of additional tubular members 27. It should be apparent, thatin FIG. 5 the principal inflatable tubular member 14 is configured forchordwise orientation of the tubular members 27. By chordwiseorientation, what is meant is a manner generally perpendicular to anorientation of the principal inflatable tubular members 14 where theprincipal inflatable tubular members 14 parallels in spanwise manner theleading edge of an aerodynamic structure such as a wing, strut or anaileron surface.

Referring to the drawings, FIG. 6 shows an alternate pattern forchordwise orientation of additional inflatable tubular members 27wherein an essentially continuous single tube forms an essentiallychordwise pattern. Fluid under pressure for inflating the additionalinflatable tubular members 27 is provided through a conduit 20. Thetubular member configuration of FIG. 6 can also be used with theadditional inflatable tubular members 27 oriented in a generallyspanwise manner with respect to a leading edge profile.

Where it is desired that the principal inflatable member 14 be inflatedin a rapid series of pulses, the use of a chattering valve can be ofvalue. While chattering in valves is a well-known phenomenon, thisphenomenon is typically avoided as undesirable, being carefully designedaround a control valve suitable for chattering operation is shown inFIG. 7.

Referring to FIG. 7 a valve 200 suitable for the practice of theinvention is depicted having accumulator 202, solenoid 204, and poppet206 sections all contained within a housing 208.

The accumulator section 202 includes a plug 210 sealed to the housing208 employing an "O" ring 212 suitably and retainably received upon theplug 210. The plug 210 and the housing 208 cooperate to define anaccumulator chamber 214. The plug 210 includes a threaded portion 216configured to engage companion threads 218 upon the body 208. Thethreaded portion functions to retain the plug 210 within the body 208and can be employed to alter the physical dimension of the theaccumulator chamber 214 by making the chamber 214 to be of greater orlesser length.

The solenoid section 204 includes an actuating coil 230 of suitable orconventional nature drivingly coupled employing a roll pin 232 to apilot pin 234. The pilot pin 234 includes a plurality of flutes 236, ashoulder portion 238, a cage portion 240 attached thereto, a ball 242and a biasing spring 244 both contained within the cage. A primary seal246 having an orifice 248 therethrough is contained within a primaryseal collar 250 and is configured for motion therewith.

The shoulder portion 238 is configured to engage in a sealing manneragainst a correspondingly configured seat 252 to prevent a flow of fluidalong the pilot pin 234 while the shoulder 238 engages the seat 252 asthe actuator 230 lifts the pilot pin 234. "O" rings 254, 256 function toseal the solenoid section 204 against undesired fluid leakage therefrom.

An inlet 260 is provided by which a fluid such as air or othercompressible gas is introduced into the valve 200. Gaseous fluid sointroduced flows into a chamber 262 and can flow along the flutes 236 ofthe pilot pin 234 to pressurize a chamber 264. A clearance of at least0.5 to 1.0 thousandth is provided between the primary seal collar 250and the valve body 208 whereby the fluid under pressure may pass intoand pressurize chambers 266, 268. The primary seal 246 functionstherefor together with the biased ball 242 to separate the pressurizedfluid from a chamber 270. This chamber 270 is operably connected with anoutlet 272 by which fluid under pressure may be passed from the valve200 to the de-icer of the invention.

The poppet section 206 includes a shuttle 280 biased employing a spring282. A threaded retainer 284 functions to retain the spring 282 withinthe poppet section 206. An "O" ring 286 functions to assure against theleakage of fluid under pressure from within the poppet section 206 pastthe retainer 284. In like manner, "O" rings 288, 290 function toforestall a leakage of fluid under pressure from within the poppetsection 206 past the body 208.

A clearance exists of at least about 0.5 thousandths of an inch to about1.0 thousandths of an inch between the shuttle 280 and the body 208 ofthe valve 200 whereby fluid under pressure in the chamber 268 may passto pressurize a pair of chambers 292, 294 as well as the accumulatorchamber 214. A lip portion 296 of the shuttle 280 seats upon a poppetseat 298 to forestall the flow of fluid under pressure from the chamber292 into the outlet 272.

The shuttle 280 includes a shoulder 300 configured to be received upon acounterbore 302 formed in the body 208. This counterbore 302-shoulder300 engagement functions to establish an upward limitation upon movementof the shuttle 280 in compressing the spring 282. A recess 304 is formedinto the shuttle 280 configured to form a low resistance pathway to airflow between the chambers 268, 294 while the shuttle shoulder 300engages the step 302.

In use the valve 200, while at rest is pressurized throughout thechambers 214, 262, 264, 266, 268, 292, 294 by the application of airunder pressure to the inlet 260. Typically this pressure is at leastabout 1000 psi (6894 kPa), more preferably 1500 psi (10340 kPa), and ifdesired as much as 2000 psi (13788 kPa) or more. Operation of the valve200 commences with activation of the solenoid 230.

The solenoid 230 lifts the pilot pin 234 seating the shoulder 238against the seat 252 thereby terminating access of fluid under pressurefrom the inlet 260 to the chambers 264, 266 and those supplied withinlet fluid under pressure therethrough. Movement of the pilot pin 234lifts the ball 242 from the orifice 248 thereby draining fluid pressurein the chambers 264, 266. The fluid pressure in the chamber 268 therebybecomes much greater than the remaining fluid pressure in the chambers264, 266 and causes thereby the primary seal 246 to lift dischargingthereby the fluid under pressure in the chamber 268 to the outlet 272via the chamber 270.

Reduced fluid pressure in the chamber 268 and the recess 304 causedthereby leaves the fluid pressure in the chamber 292 much more elevatedthan the fluid pressure in the chamber 268, and this pressuredifferential, acting upon the shuttle causes the lip 296 to lift fromthe poppet seat 298 and thereby discharges pressurized fluid from thechamber 292 and thereby the accumulator chamber 214 and the chamber 294to the outlet 272. However, shuttle 280 movement to engage the shoulder300 on the step 302 during this discharge of pressurized fluid traps asmall amount of fluid under pressure between the shoulder 300 and thestep 302 and compresses this trapped fluid. The pressure of this trappedfluid cooperates with the pressure of fluid remaining in the chamber 294to and the spring 282 to press the shuttle 234 back into a positionwhereby the lip 296 again engages the seat 298 to forestall furtherbleed down of pressurized fluid from the chambers 292, 214, and 294.

The pressure present in the chamber 268 again causes a lifting of theprimary seal 246 to again bleed pressurized fluid from the chamber 268,and the process of lifting the shuttle is thereby begun again. Thiscycling continues until the pressurized fluid contained in theaccumulator chamber 214 is substantially depleted, whereupon thesolenoid 230 is deactivated and a fluid pathway for the replenishment ofpressurized fluid in the chambers 262, 264, 266, 268, 292, 294, and 214is again established.

It should be apparent that the rate of fluid discharge from the chamber268 may be controlled to a considerably extent by the sizing of theorifice 248, as residual pressure in the chamber 264 materially assistsin reseating the primary seal 246 to forestall movement of fluid underpressure from the chamber 268 through the chamber 270 to the outlet 272.

The valve 200 therefor functions to provide a series of pulses of fluidunder pressure to the outlet 272. Where the outlet is connected to ade-icer made in accordance with the invention, these pulses function toproduce near instantaneous inflation waves within the de-icer tubeproducing thereby a series of near instantaneous distortions to the iceaccreting surface overlying the de-icer tube.

Employing the de-icer of the instant invention, deleteriousdeterioration and damage of more traditional inflatable pneumaticde-icers positioned typically external upon an outer surface of the skinof an aircraft or other object to be de-iced is avoided where suchdeterioration or damage is engendered by reason of ultra violetradiation, damage by object strike or rain or sand erosion. The de-icerof the instant invention lies sheltered beneath an outer skin having asubstantially elevated modulus and upon which ice accretes and fromwhich accreted ice is dislodged by inflation/deflation cycles of theinflation tubes.

While a preferred embodiment of the invention has been shown anddescribed in detail it should be apparent that various modifications maybe made thereto without departing from the scope of claims that follow.

What is claimed is:
 1. A valve comprising: accumulator, solenoid, andpoppet section;the accumulator section including an adjustable volumeaccumulation chamber operably connected to an outlet and an inlet for afluid under pressure; the solenoid section including a fluted pilot pinoperably connected to a solenoid and further including a caged ball andspring, the ball and spring being configured to forestall movement ofthe fluid under pressure to the outlet with the solenoid in a particularposition and the flutes being configured to provide a passage for fluidunder pressure from the inlet to the caged ball and spring while thesolenoid is in the particular position, the solenoid section furtherincluding a primary seal operably connected to a chamber associated withthe poppet section, the chamber being connected in pressurized fluidcommunication via the flutes whereby fluid under pressure may traversefrom the inlet to the chamber, and the chamber being further operablyconnected whereby fluid under pressure in the chamber acts upon theprimary seal and passes thereby to the outlet; and the poppet sectionincluding a shuttle configured for movement from a shut-off positionwhereby movement of fluid under pressure from the accumulator chamber tothe outlet is substantially precluded to a release position wherebymovement of fluid under pressure from the accumulator chamber isenabled, the shuttle being configured to, while in the release position,entrap a quantity of fluid under pressure in the chamber therebysubstantially precluding movement of the entrapped quantity to theoutlet and whereby the entrapped quantity assists in returning theshuttle to the shut-off position, the shuttle functioning thereby tooscillate rapidly between the release and shut-off positions producingthereby a chattering discharge of fluid under pressure from theaccumulator chamber.
 2. The valve of claim 1, the fluid under pressurebeing a gas.